Electrolytic process



E. GREENAWALT. FLECUULYTHPRUC APNIC/Turm min MAH. 22. :920.

Patented Apr. 5, 1921.

WILLIAM E. GREENAWALT, OF DENVER, COLRAIDO.

ELECTROLYTIC PROCESS.

Specification of Letters Patent. Patented Apr., 5.,

Application led March-22,4920. Serial No. 367,962.

`To all w hom t may concern- Be it known that l, WiLLiAM E. GREENA- y WALT, a citizen of the United States, residing in the city and county of Denver and State of Colorado, have invented certain new and useful improvements in Electrolytic Processes, of which the following is al co-pending application, Serial No. 66,621,

filed December 1?), 1915.

The process will be described more particularly in its application to the extraction of copper from its ores, to the conditions of which it is eminently7 adapted, although it is in no wise intended to limit it to this use alone.

In the electrolysis of impure copper solutions, as for example those obtained from leaching copper ores with a sulfate solution, there is always present ir'on sulfate, which injuriously affects the operation. Ferrous sulfate in the electrolyte is not particularly harmful, but the ferrie sulfate is highly detrimental.

If a solution of copper sulfate, containing ferrous sulfate, is electrolyzed, copper is deposited at the cathode while sulfuric acid and ferrie sulfate ar'e produced at the anode, as represented by the following equations The ferrie sulfate, finding its way to the cathode, combines with the deposited copper and is again reduced to the' ferrous condition, thus representing a loss of efficiency, as represented by the equation:

If, however, the ferrie sulfate can be reduced at the expense of a. comparatively cheap reducing agent, such as sulfur dioXid, then the iron in the electrolyte loses its ability to combine with the deposited-copper, while at the same time, an equivalent of acid is regenerated, as shown bythe following equation: l

a. re, (so, ,+so2+2n,o=

eresoengsop It is not easy to get the results, in practice, indicated by this reaction. The solubilityl of sulfur dioXid is quite low, and the reaction is too slow to get effective reduction. ,Even in the presence of an excess of the gas, the ferrie salts in the electrolyte will accumulate in highly injurious amounts.

In this process, to more'effectively apply the gas, it is rst combined with finely divided charcoal. Charcoal, as is well known, absorbs large quantities of sulfur dioXid. How this accomplished is not known, but whether the combination is chemical or physical, is immaterial for the ,purpose of the present process. lt is well known also that charcoal absorbs large quantities of chlorin, and the explanation usually viven is, that this is due to the'hydrogen and hydrocarbons in the charcoal. Similarly, the reaction ofi-the sulfur gas, as above indicated, m'ay be due to the hydrogen and hy- .drocarbons in the charcoal, and if the hydrogen and hydrocarbons are replenished as fast as consumed, the same as the sulfur dioXid,`the process should be carried out for some time before the beneficial effects of the charcoal are exhausted. The application of sulfur dioxid and charcoal to the treatment .of :copper ores may be carried out in any suitable apparatus. An apparatus, such as shown in the accompanying drawing, in diagrammatic section, will answer the purpose very Well, and serve to more clearly describe the invention.

The accompanyingdrawing represents a flow sheet, in diagrammatic section, of the preferred methodof operating the process,

'and a suitable apparatus for carrying it out.

'or charcoal, and 6 and 15 are agitators containing powdered charcoal, into which the l sulfur gag is introduced from the sulfur dilorid generator 19. lts flow is regulated by the valve 18.

' through the pipe 5.

The clear copper solution issuing trom the vat 1, and regulated by the faucet 2, passes through the scrubbing tower 3,` Where vthe divided charcoal, and the terric salts is eftective'ly reduced thereby. The agitator 6 has a rotary member 7, inside, so that the liquid and gas, and charcoal, are brought into intimate contact. rthe reduced liquid, separated tromthe charcoal by'means vof the grating, or tilter, 8, issues from the agitator through the outlet 9, and enters the electrolyzer 1l, containing the regulation anodes12, and cathodes 13.V When the current is turned on copper is deposited on the cathode's 13, While sulfuric acid and ferrie sulfate are produced at the anode 12. The

ferrie sulfate begins to form as `soon as the current is turned on: it is desirable, by regulatinghthe iow, to limit its amount in the cell to from 0,10 per cent. to 0.25 per cent., Which'ainounts are not particularly injurious.` From the cellv11, the solution passes through the outlet 14 into the agitator 15, where the terric salts is again rapidly and completely reduced, as in the agitator 6, and

then Hows through the outlet of the agitator,

16, into the elcctrolyzer 22, Where the action is the same as in the electrolyzer 11. This cycle iS continued until the solution is sufticiently impoverished in copper and regenh erated in acid, When-it tlovvs through the pipe 23 into vthe pump 25 and returns to the leaching vat 1 through the pipe line 24. In this Waythe cycle is repeatedr indelinitely.

There is a limit to the ability of the charcoal toiperformthe function, as above described. This is probably due to the eXha-ustion of the hydrogen, or 'hydrocarbons in the charcoal. To lengthen the use of the charcoal and to' increase its elticiency after exhaustion commences, hydrogen, or a hydrocarbon compound, from the gas generator 21, is introduced into the system with thesultur dioXid, Its amount is regulated by the valve' 20. Y

The process is also applicable to the oxidation ot sulfur dioxid to form sulfuric acid.

The concentration ot the reducing gas in the electrolyte is'an important factor 1n the reduction of the ferrie salts: it is also an important factor in the production of sul,-

-furic acid by the electrolytic oxidation ot sulfur dioxid in solution.

The charcoal acts as a concentrator of the gas, probably by occlusion, and this applies to both the sultur dioxid and to the hyterasse drogen or hydrogen containing gas. Se tar as known, the charcoal itselt' does not enter into anyof the reactions. 1t acts as an intermediary.

Manitestly other .substances besides colte and charcoal may be used for the purpose of concentrating, or occluding, the gas.

VColre and charcoal. answer the purpose, are

cheaply obtainable, and can 'conveniently be used.v l y l claim:

1. An electrolytic process Which consistsl in treating ores ot copper with an acid sol ution to dissolve the copper, electrolyzing the resulting copper solution containing` salts ot the variable valent elements to deposit the copper, applying sulfur dioXid as a reducing agent to thex electrolyte through the intermediary ot linely divided charcoal to reduce the variable valent salts from a. higher to a lower valency, and agitating the elec# trolyte in the presence ot' the charcoal and the sultur'dioxid.

2. An electrolytic process which consists in treatingv oresV of copper with an acid solution to dissolve the copper, electrolyzing the resulting copper solution containing salts ot the varablenvalent elements to deposit the metal, applying sulfur dioxid to nely divided charcoal and treating the electrolyte therewith to reduce the variable valent nsalts from a higher to a lower valency.

' 3. An electrolytic process which consists in treating' ores ot metals With a solvent for the metals, electrolyzing the resulting metal solution4 containing salts ot the variable valent elements to deposit the metals, agitating the electrolyte in the presence ot sulfur dioxid and lfinely divided charcoal to reduce the variable valent salts in the ,elec-v trolyte from a higher to a loiver valency. Y

Il. An electrolytic .process which consists in treatingores of metals with a solvent for the metals, electrolyzing the resulting metal solution Vcontaining salts of the variable valent elements to deposit the metals, and

treatin the electrolyte with sulfur dioxid and a ydrocarbon compound in the presence of charcoal to reduce the variable valent salts inthe electro-lyte from a higher to a lower valency.

5. An electrolytic process Which consists in treating ores of metals with a solvent for the metals, electrolyzing the resulting lmetal solution containing salts of the variable valent elements to deposit the metals, and

in treating ores ot metals with a solvent tor the metals, electrolyzing the resulting metal solution containing salts of the variable ies valent elements to deposit the metals, and under the action of an electric current and treating the electrolyte by agitating it in the treating the electrolyte with sulfur dioXid in presenceof finely civided carbon and a rethe presenceof a substance capable of producing gas capable of being occluded ,or con- I'noting the reaction.

centrated by the divided carbon to reduce 11. A process which consistsiin conlining the variable valent salts from a higher to a a gas over a pool of liquid, treatingthe liqlower valency. A uid of the pool with a gas by associating l 7. An electrolytic process which consists the-gas with an insoluble carrier, and elecin electrolyzing a liquid and treating the ltrolyzing the liquid.

' electrolyte by agitating it in the' presence 12.' A process `which consists in electroo a gas and a finely divided-substance calyzing a liquid containing substances in solu- 4 pable of concentrating or occluding the gas. tion which are capable of chemically react- 8. An electrolytic process which consists ing under the action of an electric current, in treating ores ci copper with an acidv soluconfining aV gas over a pool of the liquid, tin to extract the copper, electrolyzing the treating the liquid of the pool with a gas by resulting copper solution containing sa ts of associating the gas with an insoluble carrier, iron to deposit the coppertwith thesimuland intimately mixing the gas the carrier taneous conversion of the ferrous salts to the andthe liquid. ferrie salts, treating the electrolyte contain- 13. An electrolytic process Which consists ing ferric salts with sulfur' dioXid'in the in confining a gas over a pool of liquid, presence of finely divided carbon and a subtreating the liquid of the pool With the gas stance capable ofprornoting the reaction be- -by associating the gas with an insoluble tween the sulfur dioXid and the ferrie salts carrier, electrolyzing the liquid treated with 4to reduce the ferrie salts to the ferrous conthe gas, and maintaining va AElow of liquid dition. Afrom the pool to the electrolyzer and from 9. An electrolytic process which consists thev electrolyzer to the pool.

y in electrolyzing a liquid containing in solu- 14.' Anelectrolytic process which consists vtion substances capable of chemically rein confining a gas over a pool of liquid,

acting under the influence of an electric curtreating the liquid of the pool with the gas rent, confining a gas overthe electrolyte, in the presence of lan insoluble substance and treating the electrolyte with the gas in capable of concentrating or occluding the the presence of a substance capable ot' ocgas, electrolyzing the liquid, and maintaincluding or concentrating the gas in the elecing a flow of liquid from the electrodesto trolyte. the pool and from the pool to the electrodes,

10. An electrolytic process which consists and Aprogressively advancing the liquid in electrolyzing a liquid containing constituthrough a series of pools and electrolyzers.

' ents capable o reacting with sulfur dioxide WILLIAME. GREENAVALT. 

